Disk drives for data storage originally had broad requirements with respect to size or power consumption. However, with the advent of the personal computer the defacto size or form factor for disk drives was established by the space provided in the equipment by the initial user and this tended to be the dimensions of the initial commercially successful product. Subsequent devices of higher performance or storage capability were required to occupy the same space to obtain commercial acceptance. As equipment became more compact, smaller disks and reduced form factors created progressively smaller standard sizes. This has progressed thru 51/4, 31/2 and 21/2 disk sizes.
Within the form factor dimensions it has been necessary to optimize the use of space. To increase the storage density the number of disks must be maximized to achieve the optimum number of data surfaces. The electronics consequently occupies the space not required for the head-disk assembly (HDA).
Originally a single circuit card was used to provide the most economical design. However, when the HDA consumed the entire vertical height of the form factor it was necessary to have electrical components occupy the available residual volumes. Such a design is shown in Ser. No. 305,226, filed Jan. 31, 1989 now U.S. Pat. No. 5,038,239 which uses multiple cards, components mounted on flexible cable and motor driven heat dissipation and isolation provided by using portions of the unit frame.
As devices became portable and utilized battery power, minimal system power consumption became an objective. Electronic circuity consumed little power, but any function involving illumination or the driving of mechanical parts became the object of power conservation to reduce battery size and weight and/or extend the period of battery operation without recharging or replacement.